(I credit Heather Howland for setting me off on this thought process)
Ever read a really good book, closed it and thought, "I'm not worthy! I can't do that!"
Of course you can't. That was their book, not yours.
A writer friend of mine was struggling with this issue last night. I know I've dealt with it. I'm thinking other reader/writers have to have felt it too. So what do you do when you want to drop on your knees and howl you're not worthy? Learn from it.
What made that book so great? Was it the world-building or depth of plot? Maybe it was the twists in the plot itself, or setting? Maybe it was just that you had that idea too and they got there first. Learn from it.
Take your current WIP and make it better. Sure it will take work. Do you think that author didn't? If the book that had you up late and in love with it was amazing in it's word-building, then take your WIP back to the mattresses and deepen and broaden the word it's set in. Of course it's more time--your book is worth it. Was the author a genius of plot twists, then take a look at your WIP. Does your plot need twisting? Maybe not. But, if so, think about where you can add a wrinkle or divert the readers attention with a red herring. I'm not saying copy. I'm not saying to plagiarize. I'm saying to LEARN FROM IT.
Sure you might feel inadequate, but remember that was the other author's book, not yours. Remember, too, it had also been through revisions, edits, etc. Take your project, learn from the ones that awed you and make yours better.